3.分类法
        
        分类法是对同属不同类或同类而不同种的人或事物,根据不同性质进行分门别类地说明的方法。分类是人类认识客观世界的重要手段之一。分类必须遵守分类规则,使分类对象具有统一属性,依据同一分类标准,并使分类的子项相互排斥,不互相包蕴。例如:
        
        As far as political views are concerned, people fall into three categories. First are the conservative people. Conservatives are opposed to sudden or great changes. Second are the liberal people. These people are in favour of progress and reform. But their opinions often seem too idealistic. Third are the moderate people. The moderates keep everything within reasonable limits. They are more practical in this hard world. In my opinion, most people seem to belong to this group.
        
        本段把人按政治观点分为三类:保守派(conservative people)、自由派(liberal people)和温和派(moderate people),并对他们各自的特征进行了简要的分析。
        
        4.因果关系法
        
         事物变化的原因和结果是紧密相关的。如果某个现象的存在必然引起另一个现象的发生,那么,这两个现象之间就具有因果关系。因果关系包括"由果推因"(由结果去推测原因)和"由因推果"(由原因去推测结果)两种情况。因果关系符合人们的日常思维逻辑,因而在写作中得到广泛应用,常用 because, as, since, so, now that, if...then, the reason is that...等表示因果关系。例如:
        
        Of the four seasons, I like spring best. I prefer spring because it is a season of much joy and gaiety. New life bursts out everywhere. Plants wear a green coaagain and colourful flowers blossom in gardens and mountains. The old come outdoors for fresh air and the young plan for outdoor activities. Life becomes so energetic and happy.
        
        第一句为本段主题句,末句是总结句。在主题句后, 作者用了四个句子阐述自己喜欢春天的理由。
        　　
        5.比较对照法
        　　
        有意识地把两种相反、相对的事物或同一事物相反、相对的两个方面放在一起,用比较的方法加以描述或说明,指出其相同点,这种写法叫作"比较";指出其不同点,叫作"对照"。比较和对照各有不同的侧重,但两种方法经常结合使用。
        　　
         进行比较对照通常有两种方式。第一种方式采用"先A后B"的结构,即A1,A2,A3...;B1,B2,B3...。第二种方式采用"AB交错"结构, 即A1,B1;A2,B2;A3,B3...。第一种方式采用先A后B的结构实际上是把一个段落(或一篇文章)分割为两部分,先全面讲A,再全面讲 B,这样做较难收到强烈的对比效果。多数人认为第二种方式比较好,因为把对比的双方AB逐点交错,可以避免行文的单调沉闷,对比的效果也会更鲜明突出。例如:
        It is easy to be a winner. A winner can show his joy publicly. He can laugh and sing and dance and celebrate his victory. People love to be with winners. Winners are never lonely. Unlike winners, losers are the lonely ones of the world. It is difficult to face defeat with dignity. Losers can not show their disappointments publicly. They can not cry or grieve about their defeat. They may suffer privately, but they must be composed in public. They have nothing to celebrate and no one to share their sadness.
        
        这段采用先A后B的对照方式,阐述胜利者和失败者的不同特征。这种写法较易操作,但行文往往比较平淡单调。再来看看AB交错的比较方式:
        I like having a twin sister. When she’s happy, I’m happy. When she feels unhappy, I feel the same. Often, I know what she’s going to say. Sometimes, I know what she’s thinking. I like what she likes. I hate what she hates. We like the same music, the same food and the same books.
        　　
        这段采用AB交错的比较方式,阐述孪生姐妹的相同特征。这种写法较流畅自然,给读者的印象也更鲜明突出。
        　　
        6.过程分析法
        　　
         过程分析法就是把事物发展过程分为若干步骤,然后逐一加以分析说明。这种写法在说明文中使用得相当广泛。过程分析与叙事和因果关系等写法有密切关系,但彼此又有明显区别:叙事研究的对象是"What happens";因果关系研究的对象是"Why it happens",而过程分析研究的对象是 "How it happens"。例如:
        　　
        There are several steps to plant a tree. First, dig a hole large enough for the tree, but the hole should not be too deep. Second, put the tree in the hole so that it is straight. Third, put the earth back into the hole again. Push it down hard with your foot several times. Finally, water the tree well, as often as possible.
        　
        这段分析了植树过程中的几个步骤。全段层次分明,连接词语(first, second, third, finally)的使用加强了语句的连贯性。
        　　
         还必须说明的是,在实际写作中,我们很少单独采用上述几种方法中的某一种。不少段落(或文章)的写作都是综合使用各种不同的写作方法。同时还应明确,在写作中有意识地侧重使用某一种方法是有好处的。此外,上述这些说明文的写作方法在议论文中也常被采用。如何使用这些方法,写出一篇好的文章来,还需在平时认真积累,勤加练习。